In Bavaria, southern Germany, there’s something nasty lurking in the woods – a plague of caterpillars that infest oak trees. The oak procession moth and its hairy caterpillars were once extremely rare, but in Germany’s new warmer climate, this parasite is now thriving, and so far pesticides haven’t worked. Burning its nests is only a partial success, as stray caterpillar hairs can remain poisonous for several years. And not just to oak trees, to human beings as well. Georg Sperber is a retired forester with over 50 years’ experience in the forests of Bavaria. He’s concerned that the explosion of the oak procession moth is an indication that increasingly unpredictable weather patterns have altered the balance of the forest ecosystem. “For me personally, I don’t worry about the future, because I’m an old man and most things are behind me now. I’ve had a happy and beautiful life, despite the worrying developments of the last 20 years, but I have children and grandchildren and I fear they might live in a world where not just the forests have a bleak future.